Aircraft: CRJ700
Phase of flight: Initial Approach
Anomaly: Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy

While enroute; SEA Center asked what approach we were planning for CYYJ. We informed them that we would like the ILS RWY 9. We were then given a descent clearance by SEA Center of 14;000 ft and direct to OMINU at the same time. We were unfamiliar with OMINU intersection but believing it was on the approach plate (as we had just informed ATC of our request for the ILS 9 approach); and that we could quickly locate it; we began our descent and started looking for the fix on the corresponding approach plate. In doing so; we must have missed or rushed the cross verification of the set altitude in the FMA as I had set 4;000 when we had actually been cleared to 14;000. Normally a difference of 10;000 (between what I thought I had heard and the actual clearance) would have set off alarms in my head; but we were close enough to the airport at this time so that a clearance to 4000 ft didn't seem odd. After briefly looking at our charts we couldn't find OMINU intersection; so we asked ATC for its spelling. Once we received it; we proceeded direct to it. Shortly after; I noticed a traffic alert on our TCAS of another aircraft approximately 5 miles away. This aircraft was at 12900 and we were passing through about 13500 on our way down to 4000 ft as that is what I had incorrectly set. About this time; ATC called us and said 'maintain 14000'. I immediately realized the mistake and the confusing of 4000 ft for 14000 ft and we initiated a climb back up to 14000 ft. However; because we were descending at about 2500 FPM; we descended to a low of about about 12400 ft before the climb back up began. At this point; the conflicting aircraft had passed behind us. The remaining portion of the flight proceeded normally. The root cause was not using proper altitude verification procedures when setting a new altitude. The First Officer had written down 14;000 ft on his clipboard but because we got really busy in a short period of time finding and inputting a new fix; getting a spelling clarification; and beginning a quick descent relatively close to a new airport; we apparently didn't properly verify the altitude between pilots. I believed that we had done so while in the moment; but because of task saturation; it must have been missed.The two biggest items I could come up with were: First - not asking for a spelling of OMINU intersection when we first got the clearance to it. Having to search for it on the approach plate distracted both of us from executing proper altitude verification procedures. I had set 4;000 ft as that is what I thought I heard; but the FO had written down a correct 14;000 on his clipboard. Second - I was concerned with getting 'too high' during the descent to the airport; and that also contributed to rushing the verification of the 'set' altitude between pilots. Because of the distance to the airport; and that concern of being too high; I must have heard '4;000 ft' in my mind and set that accordingly. I could have done a better job prioritizing tasks. If we did indeed end up a little high on the arrival that could have quickly been alleviated with descent vectors. The workload for both of us was high as we were confused about a number of factors concerning the descent and approach. We failed to confirm the 14000 altitude with each other due to numerous other distractions. The altitude confirmation already exists in our SOP for a reason. Even in busy moments it needs to be confirmed with the other pilot. CRJ-700 flight crew reported an altitude overshoot resulted when the wrong altitude was entered into the MCP alert window. Crew cited workload and distractions as contributing.